1. Field of the Invention
The present invention relates to a video signal determination device, a video display device, a video signal determination method, and a video display method; and particularly to a video signal determination device, a video display device, a video signal determination method, and a video display method in which the type of a video signal that includes a synchronizing signal is determined.
2. Description of the Related Art
Video signal determination devices, which determine the type of video signals that contain synchronizing signals, are known in the prior art.
A video signal determination device is incorporated in a video display device (such as a projector) that can receive a plurality of types of video signals (for example, RGB signals and YCbCr signals).
An RGB signal includes color signals for the three primary colors R (red), G (green), and B (blue), and a plurality of synchronizing signals. On the other hand, a YCbCr signal (hereinbelow referred to as a “component signal”) includes a Y (luminance) signal, a Cr(R-Y) color difference signal, a Cb (B-Y) color difference signal, and a plurality of synchronizing signals.
In a video display device, the type of video signal received as input is determined by a video signal determination device. The video display device switches image processing in accordance with these determination results and thus displays the video image.
FIG. 1 is a block diagram showing a video display device.
In FIG. 1, the video display device includes: input terminal 1, RGB/YCbCr video synchronization processing circuit (hereinbelow referred to as a “synchronization processing circuit”) 2, detection circuit 3, CPU 400, scaler circuit 5, fixed pixel panel drive circuit (hereinbelow referred to as “drive circuit”) 6, and fixed pixel panel (hereinbelow referred to as “panel”) 7.
Input terminal 1 receives RGB signals and component signals. As an example, input terminal 1 receives an RGB signal from a PC, or receives a component signal from a DVD player.
Explanation here regards the video signals that are received by input terminal 1 (RGB signals and component signals).
FIG. 2(a) is an explanatory view of a component signal (YCbCr signal) having 480 rows of image lines. FIG. 2(b) is a view for explaining an RGB signal having 480 rows of image lines.
FIG. 3(a) is a view for explaining a component signal (YCbCr signal) having 720 rows of image lines, and FIG. 3(b) is a view for explaining an RGB signal having 720 rows of image lines.
FIG. 4(a) is a view for explaining a component signal (YCbCr signal) having 1080 rows of image lines, and FIG. 4(b) is a view for explaining an RGB signal having 1080 rows of image lines.
Synchronization processing circuit 2 separates the synchronizing signals from the video signal that is received by input terminal 1 (hereinbelow referred to as the “input video signal”). Synchronization processing circuit 2 provides the synchronizing signals to detection circuit 3. Synchronization processing circuit 2 further provides the input video signal, which has no synchronizing signal, to scaler circuit 5.
Detection circuit 3 includes: horizontal/vertical frequency detection circuit (hereinbelow referred to as simply “detection circuit”) 31, synchronization polarity detection circuit (hereinbelow referred to as simply “detection circuit”) 32, synchronization type detection circuit (hereinbelow referred to as simply “detection circuit”) 33, scan type detection circuit (hereinbelow referred to as simply “detection circuit”) 34, and image line number detection circuit (hereinbelow referred to as simply “detection circuit”) 35.
From the synchronizing signals, detection circuit 31 detects the horizontal synchronization frequency (“Line Freq” in FIGS. 2 to 4) and the vertical synchronization frequency (“Frame Rate” in FIGS. 2 to 4), and provides this horizontal synchronization frequency and vertical synchronization frequency to CPU 400.
Detection circuit 32 detects the synchronization polarity (“Nega” or “Posi”) from the synchronizing signals and provides this synchronization polarity to CPU 400.
Detection circuit 33 detects the synchronization type (Sep {horizontal and vertical frequencies}, CS {composite synchronization}, or GSync {Green synchronization}) from the synchronizing signals and provides this synchronization type to CPU 400.
Detection circuit 34 detects the scan type (Interlace or Non-interlace) from the synchronizing signals and provides this scan type to CPU 400.
Detection circuit 35 detects the number of image lines from the synchronizing signals and provides this image line number to CPU 400.
CPU 400 determines the type of input video signal based on the information that has been provided from detection circuit 3. More specifically, CPU 400 determines the type of input video signal based on the horizontal synchronization frequency, vertical synchronization frequency, synchronization polarity, synchronization type, scan type, and image line number.
CPU 400 further sets the signal processing corresponding to the input video signal based on the determination results, i.e., the type of input video signal.
For example, based on these determination results, CPU 400 sets the frequency division ratio and phase in an A/D converter (not shown) of synchronization processing circuit 2. By setting the frequency division ratio and phase in synchronization processing circuit 2, CPU 400 causes synchronization processing circuit 2 to execute a synchronization operation that is appropriate to the type of input video signal.
Based on these determination results, CPU 400 further sets resolution conversion data, the aspect ratio, and the color system, which indicates whether the input video signal is an RGB signal or a YCbCr signal, in scaler circuit 5. The aspect ratio is included in the determination results.
For example, upon determining that the input video signal is an RGB signal, CPU 400 sets “100% scan of the panel” as the resolution conversion data to scaler circuit 5, and in addition, performs color system settings indicating that the input video signal is an RGB signal.
On the other hand, upon determining that the input video signal is a YCbCr signal, CPU 400 sets “105% overscan of the panel” as the resolution conversion data to scaler circuit 5, and further performs color system settings indicating that the input video signal is a YCbCr signal that is to be converted to an RGB signal.
Scaler circuit 5 processes the input video signal based on the settings that have been carried out by CPU 400. By processing the input video signal, scaler circuit 5 generates a video display signal to show an image. Scaler circuit 5 provides this video display signal to drive circuit 6.
For example, when resolution conversion is set, scaler circuit 5 converts the resolution of the input video signal.
When the aspect ratio is set, scaler circuit 5 converts the aspect ratio of the image that corresponds to the input video signal into the aspect ratio that has been set.
When color system settings, which indicate that the input video signal is an RGB signal, have been carried out, scaler circuit 5 does not convert the RGB signal into another video signal format.
When color system settings, which indicate that the input video signal is a YCbCr signal that is to be converted to an RGB signal, have been carried out, scaler circuit 5 converts the YCbCr signal into an RGB signal.
Drive circuit 6 drives panel 7 based on the video display signal to form an image on panel 7.
The image that is formed on panel 7 is, for example, projected onto screen 8 by means of a projection light source (not shown).
Explanation here regards the process of determining the input video signal that is carried out by CPU 400.
CPU 400 first determines that the input video signal is an RGB signal when the synchronization type of the input video signal is “Sep” or “CS.” CPU 400 next determines the type of input video signal based on the synchronization polarity, vertical synchronizing signal, horizontal synchronizing signal, image line number, and scan type.
When the synchronization type is “GSync” (Green signal synchronization), CPU 400 first determines whether the image line number is 480, 720, or 1080.
FIG. 5 is a flow chart explaining the operation for determining the type of input video signal that is executed when the image line number is 480. The following explanation regards the determination operation when the image line number is 480 with reference to FIG. 5.
CPU 400 carries out Step 1011 when the image line number is 480 rows.
In Step 1011, CPU 400 determines whether the vertical synchronization frequency is 60 Hz. CPU 400 executes Step 1012 when the vertical synchronization frequency is 60 Hz, and executes Step 1013 when the vertical synchronization frequency is not 60 Hz.
In Step 1012, CPU 400 determines whether the horizontal synchronization frequency is 31 KHz or not. When the horizontal synchronization frequency is 31 KHz, CPU 400 executes Step 1014, and when the horizontal synchronization frequency is not 31 KHz, CPU 400 executes Step 1013.
In Step 1013, CPU 400 determines that the input video signal is an RGB of the “GSync” synchronization type, and moreover, determines that the aspect is 4:3.
In Step 1014, CPU 400 determines that the input video signal is a YCbCr signal (component signal) having a vertical synchronization frequency of 60 Hz, and moreover, determines that the aspect is 16:9.
FIG. 6 is an explanatory view showing the determination results when the image line number is 480 rows.
As shown in FIG. 6, component signal (YCbCVr signal) of 720×480 (60 Hz) is correctly determined. For an RGB signal having synchronization type “GSync,” however, the signals that are different from 640×480 (60.048 Hz) and 640×480 (59.78 Hz) cannot be correctly determined for aspect and color system (RGB signal or YCbCr signal).
FIG. 7 is a flow chart explaining the operation for determining the type of input video signal that is carried out when the image line number is 720 rows. The following explanation relates to the determination operation when the image line number is 720 rows with reference to FIG. 7.
CPU 400 executes Step 1021 when the image line number is 720 rows.
In Step 1021, CPU 400 determines whether the vertical synchronization frequency is 50 Hz. CPU 400 executes Step 1022 upon determining that the vertical synchronization frequency is 50 Hz, and executes Step 1023 upon determining that the vertical synchronization frequency is not 50 Hz.
In Step 1022, CPU 400 determines whether the horizontal synchronization frequency is 37.5 KHz. CPU 400 executes Step 1024 upon determining that the horizontal synchronization frequency is 37.5 KHz, and executes Step 1025 upon determining that the horizontal synchronization frequency is not 37.5 KHz.
In Step 1024, CPU 400 determines that the input video signal is a YCbCr signal having a vertical synchronization frequency of 50 Hz, and moreover, determines that the aspect is 16:9.
In Step 1025, CPU 400 determines that the input video signal is an RGB signal of the “GSync” synchronization type, and moreover, determines that the aspect is 4:3.
In Step 1023, CPU 400 determines whether the vertical synchronization frequency is 60 Hz. CPU 400 executes Step 1026 if the vertical synchronization frequency is 60 Hz, and executes Step 1025 if the vertical synchronization frequency is not 60 Hz.
In Step 1026, CPU 400 determines whether the horizontal synchronization frequency is 44.96 KHz. CPU 400 executes Step 1027 if the horizontal synchronization frequency is 44.96 KHz, and executes Step 1025 if the horizontal synchronization frequency is not 44.96 KHz.
In Step 1027, CPU 400 determines that the input video signal is a YCbCr signal having a vertical synchronization frequency of 60 Hz, and moreover, determines that the aspect is 16:9.
FIG. 8 is an explanatory view showing the determination results when the image line number is 720 rows.
As shown in FIG. 8, a component signal of 1280×720 (50/60 Hz) is correctly determined. However, in regard to RGB signals of the “GSync” synchronization type and of 1152×720 (50/60 Hz), aspect and color system are not correctly determined.
FIG. 9 is a flow chart explaining the operation for determining the type of input video signal when the image line number is 1080 rows. Referring to FIG. 9, the following explanation regards the determination operations when the image line number is 1080 rows.
When the image line number is 1080 rows, CPU 400 executes Step 1031.
In Step 1031, CPU 400 determines whether the scan type is Interlace. If the scan type is Interlace, CPU 400 executes Step 1032, but executes Step 1033 if the scan type is not Interlace.
In Step 1033, CPU 400 determines whether the horizontal synchronization frequency is 67 KHz, and moreover, determines whether the vertical synchronization frequency is 60 Hz. When the horizontal synchronization frequency is 67 KHz, and moreover, when the vertical synchronization frequency is 60 Hz, CPU 400 executes Step 1034. If the horizontal synchronization frequency is not 67 KHz, CPU 400 executes Step 1035, and if the vertical synchronization frequency is not 60 Hz, CPU 400 executes Step 1035.
In Step 1034, CPU 400, determines that the input video signal is a YCbCr signal in which the vertical synchronization frequency is 60 Hz and the scan type is “Non-interlace,” and moreover, determines that the aspect is 16:9.
In Step 1035, CPU 400 determines that the input video signal is an RGB signal whose synchronization type is “GSync,” and moreover, determines that the aspect is 4:3.
In Step 1032, CPU 400 determines whether the horizontal synchronization frequency is 27 KHz, and moreover, determines whether the vertical synchronization frequency is 48 Hz. If the horizontal synchronization frequency is 27 KHz, and moreover, if the vertical synchronization frequency is 48 Hz, CPU 400 executes Step 1036. If the horizontal synchronization frequency is not 27 KHz, CPU 400 executes Step 1037, and if the vertical synchronization frequency is not 48 Hz, CPU 400 executes Step 1037.
In Step 1036, CPU 400 determines that the input video signal is a YCbCr signal in which the vertical synchronization frequency is 60 Hz and the scan type is “Interlace,” and moreover, determines that the aspect is 16:9.
In Step 1037, CPU 400 determines whether the horizontal synchronization frequency is 28 KHz, and moreover, determines whether the vertical synchronization frequency is 50 Hz. If the horizontal synchronization frequency is 28 KHz, and moreover, if the vertical synchronization frequency is 50 Hz, CPU 400 executes Step 1038. If the horizontal synchronization frequency is not 28 KHz, CPU 400 executes Step 1039, and if the vertical synchronization frequency is not 50 Hz, CPU 400 executes Step 1039.
In Step 1038, CPU 400 determines that the input video signal is a YCbCr signal whose vertical synchronization frequency is 50 Hz whose scan type is “Interlace,” and moreover, determines that the aspect is 16:9.
In Step 1039, CPU 400 determines whether the horizontal synchronization frequency is 33 KHz, and moreover, determines whether the vertical synchronization frequency is 60 Hz. If the horizontal synchronization frequency is 33 KHz, and moreover, if the vertical synchronization frequency is 60 Hz , CPU 400 executes Step 1040. If the horizontal synchronization frequency is not 33 KHz, CPU 400 executes Step 1041, or if the vertical synchronization frequency is not 60 Hz, CPU 400 executes Step 1041.
In Step 1040, CPU 400 determines that the input video signal is a YCbCr signal in which the vertical synchronization frequency is 60 Hz and in which the scan type is “Interlace,” and moreover, determines that the aspect is 16:9.
In Step 1041, CPU 400 determines that the input video signal is an RGB signal whose synchronization type is “GSync,” and moreover, determines that the aspect is 4:3.
FIG. 10 is an explanatory view showing the determination results when the image line number is 1080.
As shown in FIG. 10, a component signal of 1920×1080 (48/50 Hz) and 1920×1080 (60 Hz ) is correctly determined. However, signals, which differ from 1920×1080 (49.975 Hz) in an RGB signal in which the synchronization type is “GSync” , are not correctly determined for aspect or color system.
In addition, JP-A-2005-167676 discloses a video signal determination device that is incorporated in a projector.
This video signal determination device calculates the probability that the input video signal is an RGB signal (RGB probability) and the probability that the input video signal is a Y/color difference signal (color difference probability). This video signal determination device compares the RGB probability and color-difference probability to determine whether the input video signal is an RGB signal or a Y/color difference signal.
In the determination method that is executed by CPU 400 that is shown in FIG. 1, when an RGB signal is applied as input in which the synchronization type is “GSync” and the timing of the horizontal synchronization frequency and vertical synchronization frequency approaches that of a component signal, the aspect is forcibly determined to be 16:9, and the color system is determined as YCbCr.
As a result, an RGB signal in which the synchronization type is “GSync” is not accurately determined. In addition to this erroneous determination, the image cannot be properly displayed in accordance with the input video signal.
In such cases, the user must either switch the aspect and color system manually, or set the synchronization type of the RGB signal to “Sep” or “CS.”
The determination method that is described in JP-A-2005-167676 requires complex processing for both calculating RGB probability and color difference probability and then determining the type of input video signal that is based on these calculation results.